Reenable thinlto on android tot bot, to see if it works again.

Bug: 887272
Change-Id: Ia9e6ddf68f47f0dceb8616582969199a90d52912
Reviewed-on: https://chromium-review.googlesource.com/1257202Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595940}

build/config/compiler/compiler.gni

@@ -52,7 +52,8 @@ declare_args() {
   # Enables support for ThinLTO, which links 3x-10x faster than full LTO. See
   # also http://blog.llvm.org/2016/06/thinlto-scalable-and-incremental-lto.html
   # TODO(https://crbug.com/887272): Reenable on is_android && is_official_build
-  use_thin_lto = is_cfi
+  use_thin_lto =
+      is_cfi || (is_android && is_official_build && llvm_force_head_revision)
 
   # Tell VS to create a PDB that references information in .obj files rather
   # than copying it all. This should improve linker performance. mspdbcmf.exe